Red Sox shortstop Stephen Drew will man second base for the Yankees after he was acquired for Kelly Johnson on Thursday.

Both additions are viewed as offensive upgrades to a club with designs on October.

But the bigger mystery is whether they can instantly adapt to new positions.

Obtained from the Red Sox for Kelly Johnson and $500,000, Drew – a career shortstop — will switch clubhouses today and become the Yanks’ regular second baseman, with Brian Roberts due to be designated for assignment.

Prado, acquired from Arizona for slugging catching prospect Peter O’Brien, is expected to be the regular right fielder, though he’s played just two big-league innings at the position in nine seasons.

“Do I think our club is better now, the answer is yes,” said Yankees general manager Brian Cashman shortly after the 4 p.m. deadline. “But talk is cheap. We have to go out and prove it.”

Cashman had already stabilized an injury-wracked starting staff with July trades
for Brandon McCarthy and Chris Capuano, and also dealt for switch-hitting third baseman Chase Headley.

And other right-handed hitting outfield options were either too costly (Marlon Byrd), held onto by their clubs (Josh Willingham) or were dealt elsewhere (Chris Denorfia).

“I was very engaged with every player we felt we could improve our roster,” Cashman said without mentioning specific names.
“We had a lot of conversations [and] we saved some assets that hopefully will be in play for us down the line.”

Plus, the right-handed hitting Prado is signed through 2016 and the Yankees get a preview look at the lefty-swinging Drew – an impending free agent and a candidate to replace retiring captain Derek Jeter at shortstop next season.

“It creates an opportunity for everybody to get to know each other better,” said Cashman, who put Headley into the same category at third base. “We’ll all get an advanced look at each other prior to the free-agent market.”

But the deals were made mostly with the present in mind.

“Clearly, the offense has been more and more of a problem,” Cashman said of a Yankees lineup that has scored 30 fewer runs (429) than it has allowed (459), yet remains in contention in the AL East and the second AL wild card at 55-52.

Cashman landed Prado, 30, a .290 career hitter batting .270 this year with five homers and 42 RBI. Mostly a third baseman and second baseman, Prado has played some in left field.

Though the Yanks will make use of his versatility, Prado is mainly asked to bolster right field, where Ichiro Suzuki is viewed as a part-timer and Carlos Beltran (bone spur) is limited to being a designated hitter.

Drew, 31, was pitched as a possible second base option by agent Scott Boras as his client hovered in free-agent limbo this past off-season.

After hitting .253 with 13 homers and 67 RBI for the 2013 world champion Red Sox, Drew rejected Boston’s one-year qualifying offer and remained unsigned until Boston agreed to a contract in late May.

But Drew only became a realistic fit for Cashman on Thursday, when the Red Sox began swapping big-ticket pitchers Jon Lester (Athletics), John Lackey (Cardinals) and Andrew Miller (Orioles) to other contenders.

“I sent [Boston GM] Ben Cherington a text,” and the rivals quickly completed their first trade since 1997, when the Sox shipped catcher Mike Stanley to the Bronx.

Offensively, Drew’s awful start has resulted in a .176 average in 131 at-bats. But he’s hitting .267 (12-for-45) over his past 13 games with two homers, six RBI and an .888 OPS.

As for Drew’s 955 career games at shortstop and none at second base, “We’re asking him to accept this challenge and we believe his ability will allow it,” Cashman said, though he admitted to meetings where club officials shook their heads and asked: “Can he do this?”
August deals might be made for players who clear waivers, but Cashman was content with the moves he swung in July.